Yankee drier profiler and control

ABSTRACT

A coating system, a paper machine, and methods of their use are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional ApplicationSerial No. 61/711,462 filed Oct. 9, 2012.

BACKGROUND OF THE INVENTION

The present disclosure relates to Tissue and Towel paper making machinesand, more specifically, to a process of coating a Yankee dryer and theCreping process.

A Yankee dryer is a pressure vessel used in the production of tissuepaper. Yankee dryers are primarily used to remove excess moisture frompulp that is about to be converted into paper. The Yankee cylinder canbe equipped with a creping blade (in combination with a doctor blade)where the cylinder is sprayed with adhesives to make the paper stick.Creping is done by scraping the dry paper off the cylinder surface withthe Doctor Blade and thereby creping the paper at the Creping Blade. Theresulting crinkle is controlled by the strength of the adhesive,geometry of the Doctor blade/Creping Blade combination, speed differencebetween the Yankee and final section of the paper machine and paper pulpcharacteristics.

Currently, the actual lubrication of the doctor blade over 23 zones(number of spray nozzles×6 inches) is accomplished based on theprinciple of delivering the release coating at a constant pressure to acommon manifold. Based on this principle, achieving common flow rate forall nozzles is assuming a common pressure on the manifold equals acommon flow rate at the spray nozzles resulting in a gross assumption.Thus, the principle implies the friction loss for all 23 nozzles willalways be the same and that all of the nozzles and piping deliverymechanisms were created under exact manufacturing practices and willnever show any effect due to wear. If this were the case, everythingmight work well for a day or two but in reality, 23 or more nozzles on asingle manifold will not perform well for very long. Minor differencesin manufactured parts as well as the current state of buildup in thepiping will cause variances in friction losses thereby changing theindividual flow rates dynamically. Also, wet spots on the product beingprocessed at the Yankee dryer will have a tendency to absorb differentrates of release coating thus changing the residual coating level. Thischange cannot be compensated for on a single manifold control unless anoperator opens or closes a spray valve manually. Detecting the problemand correcting the problem, from a human standpoint is only accomplishedif the problem has become catastrophic. There is a need to address thecoating release residual level which can change due to wet streaks inthe web or the improper flow control at each nozzle.

SUMMARY OF THE INVENTION

A coating system and method thereof to take control and correct theapplication of the release coating chemistry to insure: the releasecoating chemistry is at the proper mix ratio as programmed by a recipeset point which may be adjustable by the operator, the release coatingis being applied in the proper thickness across the Yankee dryer surfaceat all times, increase and decrease the proportional valves at eachnozzle in order to compensate for, and maintain, a constant flow rateindependent from variations in supply pressure, increase and decreasethe flow rate in order to compensate for variations in production speed(ft/min), detect and report graphically areas that are not coatedproperly if the system cannot correct a specific problem, provide agraphical view of the concurrent production as to speed, flow rates,release coating thickness, and Yankee temperature profile over theentire surface, extend the life of the creping and doctor blades,decrease maintenance on the spray nozzles, and translate the productiondata obtained into clear visual results and warn operators in an audio,and visual (graphical) manner of process problems.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a spectrum from 200 nm to 1000 nm under ultraviolet longwave spectrum wherein water is used as a reference;

FIG. 2 shows a spectrum wherein water is used as a reference verses acomponent of 100% release oil

FIG. 3 shows a spectrum wherein water is used as a reference verses acomponent of 100% MAP;

FIG. 4 shows a spectrum wherein water is used as a reference verses acomponent of 100% coating;

FIG. 5 illustrates the Yankee dryer coating system;

FIG. 6 illustrates a laser-lased method of measuring a coating thicknessand topography;

FIG. 7 illustrates a means of using chromatic aberration according tothe present disclosure;

FIGS. 8-12 illustrate a variety of creping blade monitoring schemesaccording to the present disclosure;

FIG. 13 illustrates a roll-up inspection station according to thepresent disclosure; and

FIG. 14 illustrates proportional control of release and coatingchemistry according to the present disclosure.

DETAILED DESCRIPTION

The present disclosure provides for Yankee Dryer Release CoatingApplication. An aspect of the disclosure to realize the disability ofthe single manifold type of control with its indiscriminate applicationof release coating is based on an averaging response by a single controlpoint mechanism. However, through the implementation of individualcontrol over each spray nozzle, one can tailor each nozzle outputprecisely and independently over the entire Yankee dryer surface. Forexample, each nozzle may be independently controlled to servo its flowrate to a master flow rate set point. Variations due to friction losses,pressure differentials, and spray nozzle wear, etc. can be compensatedprecisely. Thus, this would be accomplished in having each nozzlecontrolled by its own microcontroller, proportional flow rate controlvalve, precision flow rate meter, and spray nozzle. Each spray flow ratewould be independently controlled to the master set point within <=1%(+/−0.05%). There will however be a need to implement corrections toindividual nozzle flow rates based on residual coating thickness,detected after the release, in order to prohibit wear on the creping anddoctor blades. The maximum allowable deviation from the master set pointflow rate will be a programmable limit at a maximum value of about 10%.Thus verifying the release coating thickness on the Yankee dryer may becritical in order to implement the automatic corrections in theindividual flow rates in order to correct for wear of the creping blade.

A further aspect of the present disclosure relates to measuring thedifference and detecting the Yankee dryer release coating thickness andcoating quality using an industrialized Ultraviolet VisibleNear-Infrared (UV-VIS-NIR) spectrometer. The present disclosure providesan industrialized UV-VIS-NIR spectrometer which can optically analyzethe release coating thickness as well as the accuracy of the solutionapplied. The UV-VIS-NIR spectrometer may be driven back and forth (leftto right) across about 3-4 inches from the Yankee dryer surface,yielding the actual coating thickness for each 0.02 inch of linearmovement across the surface. A different scanning spectrometer willyield an accurate temperature profile, 50 points per inch, for theentire surface. This data may then be displayed in a graphical manner ona display monitor so that an operator can, at a glance, correlate thetemperature and coating thickness imaging to process problems. Whereinerror/fault regions will have their positions marked for example in red.If a problem is beyond the capability of being solved by the computercontrol system or its programmable limits as set, alarms may sound andmarkers may be placed on the screeen to show the location of the erroras well as a text message to describe the type of error involved. Thisalarm, as well as all alarms, are date and time stamped for permanentrecording on the system hard drive. Thus the system of the presentdisclosure saves all running data, maintanence records, and all alarmsannunciated with date and time stamp continuosly. These records arepermanent and can be reviewed with our data viewing software.Maintanence reports may be viewed daily and since the machine keepstrack of its own maintanence issues, maintanence issues are scrolled inthe maintanence issue window as they are needed to be performed.Therefore, the machine may tell the user if it requires maintanence.

Regarding the water used as a reference in measuring the difference anddetecting the Yankee dryer release coating thickness and coatingquality, a water softening system with dual tanks may be used thatrecharging can be accomplished without interruption. Untreated water mayaffect the manifolds, spay nozzles, valves, etc. of the coating system,thus the need to remove the CaCO₃, MnO, Fe₂O₃ that may cause sideeffects, or otherwise, chemistries you are not trying to effect on theprocess such as precipitations, gumming or unexpected catalyzedpolymerizations. The coating system may use less than 200 gallons perday. A water softening system produces water that has a sodium (Na)based chemistry. Although softened water is not as good as distilledwater, it may be practical. It will remove the calcium (Ca), Iron (Fe),manganese (Mn), and vanadium (V), and other metal ions prevalent inuntreated water. The use of treated water will provide long termpredictability in applying the release coating of the presentdisclosure.

The main system control used in the present disclosure may consist of aNEMA 12 enclosure which will house the 8 core Windows 7 based computerwith the specific control software, 22 inch wide screen monitor, excesselectronic circuitry, a Freon based 4000 BTU air conditioner to cool thesystem, internet radio communications for factory personnel 24 hour aday 7 days a week, power supplies and an interface mechanism tocommunicate to the in-plant programmable logic controller (PLC) such asEthernet. The main system may have numerous extra input/output (I/O) andanalog I/O available for future expansions.

The main system control may be made available as a remote unit, remoteoperator's station, which takes up a fraction of the space and works inparallel with the main station. Essentially consisting of but notlimited to a monitor, key board and mouse with all of the main controlbuttons.

The release coating application assembly of the present disclosure mayconsist of a manifold assembly which may be installed in parallel to anexisting system. If such system fails, the existing system will continueto run until the manifold assembly system is back up and running, thusresulting in no down time. The manifold assembly may consist of but notlimited to the following: a main manifold wherein all wetted parts arestainless steel, a manifold conduit prewired in water proof conduit,twenty-three proportional flow rate valve ASCO 202 Series pulse widthmodulated drive, twenty-three Cole Parmer EW-32718-06 flow sensor flowrate amplifier and twenty-three quick disconnect spray nozzle byspraying systems.

A release coating inspection system of the present disclosure mayconsist of a temperature and humidity controlled NEMA 12 enclosure whichwill travel back and forth on a lubricated linear ball and guideassembly. The linear ball and guide bars may be made of stainless steelfor the shafting with powder coated support beams. The linear ballscrews may be continuously lubricated in order to dissolve any build upof sprayed chemicals. The assembly can handle dirty environments andambient temperatures up to 250° F. The radiant intensity controlled UVand variable power controlled incandescent light sources for thespectrometer as well as two infra-red temperature cameras for completetemperature profiling of the Yankee Dryer surface. A solid staterefrigeration and heating system to keep the enclosed sensors at aconstant 70° F. all year round. A replaceable desiccation stem to keepmoisture out of the spectrometer and cameras. A 200 nm through 1000 nmspectrometer which will cover from ultra violet through the entirevisual range and into the near infrared wherein the resolution of thespectrometer is 0.3 nm. A stepper motor drive and electronics forpositioning the inspection station to within about 0.001 inch.Quadrature encoder to track the position of the Yankee dryer to withinabout 0.001 inch thus requires the positions of defects/errors in theprocess to be tracked. Clean filtered and electronically monitored airpurging pump to keep the lenses clean. Plant air is dirty and costly,thus controlling the quality of the purging air is enhanced by thepresent system as well as the use of electronics to monitor the systemfor proper flow and filter condition. A master pulsed type flow meterand pressure gauge for the incoming process water. A water purificationsystem which consists of 5 micron filters and carbon filters. Ingeneral, PLC's are handling what they can do. However PLC's cannotanalyze millions of data items per second, nor can they evaluateworkable solutions for problems involving trillions of calculations.Thus, a personal computer (PC) on the other hand was made for thispurpose. Software written for the PC may also provide solutions in agraphical and text manner that provide clear cut instructions to theoperator. The advantage is the ability to go through a multitude ofcomplex problems, involving millions of equations, in the time it takesa PLC to loop once through its program. The types of problems withproduction processes, which have not been handled thus far with PLCsolutions are difficult, thus with the present disclosure those problemscan be solved using PC based systems which is specialized in complexproduction problems.

Advantages of the present disclosure include a coating system and methodthereof to take control and correct the application of the releasecoating chemistry to insure: the release coating chemistry is at theproper mix ratio as programmed by a recipe set point which may beadjustable by the operator, the release coating is being applied in theproper thickness across the Yankee dryer surface at all times, increaseand decrease the proportional valves at each nozzle in order tocompensate for, and maintain, a constant flow rate independent fromvariations in supply pressure, increase and decrease the flow rate inorder to compensate for variations in production speed (ft/min), detectand report graphically areas that are not coated properly if the systemcannot correct a specific problem, provide a graphical view of theconcurrent production as to speed, flow rates, release coatingthickness, and Yankee temperature profile over the entire surface,extend the life of the creping and doctor blades, decrease maintenanceon the spray nozzles, and translate the production data obtained intoclear visual results and warn operators in an audio, and visual(graphical) manner of process problems.

As known in the art, applying more release coating in an area to solve acoating thickness problem may solve the thickness problem but may causeother problems. If the coating is too thin, it could be caused by a wetspot on the web. Thus, the present disclosure addresses correcting thecoating thickness problems known in the art resulting in improvedrelease coating thickness and ratio. However, wet spots in the web willabsorb more coating than normal making the coating thinner. This mayalso cause a slightly cooler area since the evaporating water andabsorbed coating will remove a proportional amount of heat. Temperaturelosses may be greater in those areas showing a corresponding decrease intemperature left as a ghost image on the Yankee dryer. Thus increasingthe release coating flow rate in that area may have a good effect.However, at some increased flow rate of release coating, one may expectthe existing quality problem, due to a wet spot, to worsen. Limits maybe implemented to control how much the system can change the flow ratesat each nozzle. Therefore, the Yankee dryer temperature profile obtainedfrom the scanning camera may allow the PC to confirm, along with thespectrometer data, that this is a problem caused by a wet spot generatedat the head box. The system of the present disclosure may graphicallyshow the operator where the wet spot is located on the web allowing thesystem to address the specific problem.

In order to determine the thickness of the release coating of thepresent disclosure a first determination of the exact thickness of therelease coating solution on the Yankee dryer surface must be made byfirst obtaining the exact solution spectrum and derive from it theconcentration of individual components in that solution. In other words,the solution make up of MAP, coating, and release oil in terms ofpercent concentration of each in the final solution prior to sprayingthe mixture onto the Yankee dryer surface. It is important to have apredetermined curve of the desired solution spectrum, determined from arecipe. This recipe spectrum can be created from known spectrums foreach individual component at varying concentrations in purified water.

Once the spectrums have been obtained for each pure component atdifferent concentrations which are in the useful concentration range,the pixel data (0.3 nm) may be used from the spectrometer of thosevarying concentration spectrums, which were taken at a known radiantenergy of short wave UV, apply the equation of y=mx+b for two knownconcentration points, plot any pixel response at any concentration forthe given component thereby creating a new spectrum for that componentat any concentration. Wherein y=the pixel response at (x) concentrationat a constant radiant power at short wave UV (peak @ 365 nm);m=slope=(y2−y1)/(x2−x1); b=(offset)=y2−(x2*m).

Next, obtain the same reference curves at different temperatures of thesolution for each component wherein this is also used to correct theindividual reference spectrums, mentioned above, for the pixel responseof each component under varying temperatures. Temperature may affectchanges in the absorption spectra because the component molecules willbe at different energy states at different temperatures. This will becalculated per pixel (0.3 nm) and applied to the spectra above so thatnew spectra can be calculated for the above reference spectra at thecalibrated concentrations with a known radiant power UV. Again applyingthe equation of: y=mx+b for each pixel wherein, y=the pixel response atx temperature for each component at the known concentration for eachcomponent that we used in the equation above; m=slope=(y2−y1)/(x2−x1);b=(offset)=y2−(x2*m). This will now allow recalculation any referencespectra of any pure component solution for any concentration (over therange of solutions concentrations tested) and correct it for the properresponse over any temperature variations expected in the realapplication of this device.

Next, correction for variations in the Radiant Power applied to thesolution, again at the known concentrations used above is done. As thelight source ages, the intensity of the source may vary. A spectrometerwill also monitor the spectral energy of the UV source to correct theoutput power over the life of the source. However variations in radiantpower per pixel will occur. Evaluating the known concentrations of thepure components at the already known concentrations, and by varyingradiant power levels one can again apply the equation: y=mx+b to thecalibration spectra above per pixel (0.3 nm). Now, varying the radiantUV power intensity with a high and low level changes can be obtained inpixel response due to changes in radiant power over the range ofvariance expected from the UV source. Wherein y=mx+b for each pixel;y=the pixel response at x radiant power level for each component and atthe known concentration for each component that we used in the equationabove; m=slope=(y2−y1)/(x2−x1); b=(offset)=y2−(x2*m).

Finally, one can determine and plot a new spectrum from stored data andby sequentially applying the equations above. Based on real time sensorinputs for temperature and radiant power levels, one can create newspectra that will modify the stored reference spectra, which willreflect the actual variances in those spectra caused by the real timesensor data for temperature and radiant power levels of the light sourceand at any concentration of this component in water.

This may be accomplished for each individual component needed in arecipe of components. For example, the corrected spectra for MAP,release, and coating would be calculated and stored in memory. Thesereference spectra would be continuously recalculated to reflect changesin temperature and radiant power.

As shown in FIGS. 1-4, while a VIS and NIR spectrometer may be used tomeasure the water as a reference as well as components such as but notlimited to 100% release oil, 100% MAP and 100% coating, detectability isshown more exactly using a UV spectrum.

Determining the spectra of the release coating mixtures/solutions for arecipe consists when a recipe is needed for production, a mixture of thethree components is blended in order to accomplish proper lubrication ofthe creping blade as well as provide the proper release of the tissueproduct from the Yankee Dryer. Different mixes of the raw componentsabove are blended to accomplish the same tasks but need different mixratios for different types of tissue being processed. A means ofcalculating a dynamic master recipe spectrum, as a reference spectrum inmemory, is required in order to evaluate the actual blended recipe inreal time. This recipe spectrum would characterize the ideal mixture ofcomponents but also be dynamic in nature so as to be modifiedcontinuously by recalculating and thereby compensating for temperaturechanges and a varying radiant power.

Establishing the mechanism to recalculate the single component curvesfor temperature, radiant power, and individual component concentrationmay be done using the method above. By taking the recipe at knowncomponent concentrations for each as described per the recipe, theresulting curve to be calculated as a master recipe can be put togetherbased on each pixel response at a given wave length and also on thepercentage of each component in the recipe solution. For example, if theMAP component is to be added at a final concentration of 4%, the releasecomponent at 5.5%, and the coating component at 10%, then for a givenpixel response for each, corrected for temperature and radiant power,and at the stated concentration, one can easily calculate the newexpected pixel response for each pixel of the master recipe spectradynamically, for the level of the components in that recipe at theirconcentration levels and corrected for temperature and radiant power.

Variations in real time component concentrations may occur due tomechanical issues encountered in normal production practices. Aspectrometer would be used in the raw feed supply of the made up recipein order to measure the accuracy of the scanned real time spectrum ofthat raw feed recipe. By analysis of the real incoming spectral data andcomparing it to the stored master recipe spectra, one can mathematicallydetermine the true concentrations of the mixture. With this, one canaffect a proportional change in the mix ratio in order to correct theseerrors in the final solution of the components recipe being made in realtime. The pump speeds and flow rates for each component can be adjustedin order to effect the changes needed in order to bring the actualproduction mix back into the recipe specifications. The actual analysisis based in the integration of the pixel response over the spectralrange in order to receive a percentage error, while a derivative valueof the pixel data, for a given wave length range, will yield particularcomponent concentration errors. Again, discrete derivatives will bepeculiar to one mix component more so than other components for a givenwave length and the integration of the pixel data will yield the overallpercentage error of the mixed ratios. In order to acquire the depth ofthe residual recipe left on the Yankee dryer, an exact composition ofthe real time solution must be known prior to application of the mixtureonto the Yankee dryer surface. Knowledge of exactly what the mixture iscomposed of and how much of each individual component is in the appliedsolution is needed. Then one can evaluate how much of each component theprocess used after the creping blade has released the tissue. As some ofthe aspects of the present disclosure is to increase the life of thecreping blade as well as increasing the quality of the tissue product,the ability to analyze the residual left over coating is an importantaspect of the present disclosure.

Determining residual release coating thickness on the Yankee dryer afterthe creping blade release consists of the ability to determineindividual component concentrations through the mathematical evaluationof the spectra above, these methods can now be used to determine notonly the residual composition after the creping blade, but alsodetermine the thickness of the coating as well.

While emitting a quantum amount of UV energy with a peak at 365 nm,controlled by measuring and adjusting the radiant power through controlcircuitry, the stored reference spectra as described earlier, and thesame methods as described above are determined by correcting fortemperature, radiant power and concentration of each, the calculatedthickness of the residual release coating can be used. This will bedetermined by integrating the absorption response per pixel across thespectra. Since the recipe of components used, during the manufacturingprocess all absorb UV energy, the amount of UV energy absorbed by theresidual, left over, release coating may be readily detectable and mayvary in proportion to this residual thickness. This residual thicknessand the residual component concentrations may then be correlated to thelinear movement across the Yankee dryer surface by a linear ball screwdevice in order to develop a complete profile of the Yankee dryersurface in real time. Minute changes in the integrated absorptionresponse, being proportional to the thickness of the residual coatingbut also yielding detectable component concentrations, should allow oneto vary the original recipe in order to effect quality enhancements inthe manufacturing of the tissue product in real time. By passing thespectrometer back and forth along the Yankee dryer surface one will beable to develop a surface profile as well as pin point problems inmanufacturing such as correcting deficient areas of release coating byadjusting the recipe, changing flow rates, and warning the operator ofproblems elsewhere in the process that could affect quality or downtime.An example of the latter would be a wet spot cause by a vacuum problemon the felt or a dry spot caused by insufficient fiber content in thestock being fed at a location in the head box.

Determining Residual Release Coating Thickness on the Yankee Drier afterthe Creping Blade Release

Since we have established the ability to determine individual componentconcentrations through the mathematical evaluation of the spectra above,these methods can now be used to determine not only the residualcomposition after the creping blade, but also determine the thickness ofthe coating as well.

Since we are emitting a quantum amount of UV energy with a peak at 365nm, controlled by measuring and adjusting the radiant power throughcontrol circuitry, we can use stored reference spectra just as describedearlier. Using the same methods as described to determine, by correctingfor temperature, radiant power and concentration of each, the calculatedthickness of the residual Release & Coating. This will be determined byintegrating the absorption response per pixel across the spectrum. Sincethe recipe of components used, during the manufacturing process allabsorb UV energy, the amount of UV energy absorbed by the residual (leftover) release & coating will be readily detectable and will vary inproportion to this residual thickness.

This “thickness” at this point is not dimensional. It relates only tothe density of the coating in terms of the amount of each componentpresent. We need to know the moisture content in order to give us avolume leading to a better idea of thickness and its topographyinformation to give us depth information.

Measure the Moisture Content of the Residual Yankee Drier Coating

A liquid moisture-detecting camera will be used in determining theactual moisture content of the residual coating. Since the moisturecontent determines the hardness of the coating, a coating with littleresidual moisture content will be harder and denser than a coating witha greater concentration of water embedded. If the moisture content ofthe coating is too little or too great, degradation of the coating willoccur in the form of cracking and its ability to give release of thetissue at the creping blade and improper adhesion at the Roll-Nip point.

In determining the actual moisture content of the Release Coating, wewill take advantage of the absorption of liquid water in the 1900 nm to1950 nm range. The moisture content of the coating will be non-linearbut proportional to the formula; a*v1+v2+b*v3 where a+b=1. In theformula, v1 is symmetrical stretch of the H—O—H water molecule bondingdistance of the hydrogen atoms from the Oxygen atom at its center. Thev2 is a measure of a changing bond angle from the normal 104.4 degreesat 20 C. Finally, v3 is the asymmetrical stretch where the Hydrogenatoms are in stretch mode but one Hydrogen atom is stretching toward theOxygen atom and the other away from it. There are many absorption bandsfor liquid water; however, we have chosen this band, even though it isof low energy, because it is more peculiar to water. The detectedsignals will reflect less interference from compounding absorption withother molecules in this spectral region. The intensity of the IR sourcefor this camera will be varied to correct for the emissivity of the realtime coating conditions and the ageing of the filament over time.

The calculations for the derivation of the actual coating thickness atthis point, and with the methods described above, are rather intense.Mathematically determining coating thickness strictly from methodsdescribed thus far would at best implement a theoretical component,which could still lead us towards making incorrect process changes. Fromthe implementation of the above methods, we will yield a good averageddetermination of the Coating thickness across the Yankee surface.Coupled with the Moisture Camera readings, a very accurate Coatingdensity can be obtained. A very accurate Coating temper can also beimplied which tells us much about the quality of the coating and itsability to effect adherence of the tissue at the Roll-Nip point and itsability to release the tissue properly at the creping blade. It alsowill give us a good determination of the average derived topography ofthe over entire Yankee Drier Surface. However, knowing the exacttopography of the Coated Yankee Drier surface is desirable in order todetermine blade wear points and pin pointing defective release points atthe Creping Blade as well as, defective adhesion points at the roll-nip.

Measure the True Topography of the Residual Yankee Drier Coating

In order to evaluate the coating properties reliably, knowing the exacttopography of the coating, one must have an acute understanding of howthe coating surface affects the functionality of the coating. Forexample; even if the coating properties, as revealed through theanalysis of the methods described thus far, indicate a perfect moisturecontent, proper temper, adequate curing, etc., the height or thicknessat a particular location on the Yankee Drier may be insufficient due togouging by the Creping Blade mechanism. The instantaneous pressure alongthe length of the blade may be too high or too low. This can lead to acondition where the Creping Blade may modulate; self resonate, or createthe condition commonly called “Chattering” across the Coated surface ofthe Yankee Drier. Imperfections in the tissue web being processed canlead to the same types of defects. Therefore, obtaining the exact shapeof the Yankee Surface Coating is required.

The surface of the underlining Yankee machined surface is alsoimportant, not only from the aspect of maintenance, but due to theobvious fact that any imperfection in the machined Yankee metal surfacewill also replicate itself in the applied coating as well.

The device created to measure this will employ a line generating diodelaser at 635 nm, a Plano-convex lens at 12.5 mm focal length in order todiverge (+/−45 degrees) the emitted rays back to straight and parallelin the original axis of emission. It will also employ a series of threeoptical slits measuring 10 microns×1 mm spaced 0.250 inches apart inorder pass these focused parallel coherent beams of light onto thecoated surface. The angle of emission when applied to a perfectly flatsurface will effect reflection at an acute angle exactly equal to theangle of emission but away from the angle of emission. In other words,if the angle of emission hits a perfectly flat reflecting surface at anobtuse angle of 120 degrees the acute angle of reflection will be 90degrees minus 30 degrees (90+30=120), which equals 60 degrees acute.When this ray reflects, it should land at a predictable location at someknown distance from the reflected surface. We will be using a 3000 pixelline-scan camera to detect this reflection. As the surface becomes lessflat, this perfect angle will disperse from the corresponding predictedpixel location. It will be received as distributed (a dispersion)amongst the adjacent pixels relative to the amount of imperfections onthe reflecting coated surfaces. A modulated surface topography will showup on the CCD pixels of the Line-Scan Camera as modulated. Performingstandard Fast Fourier Transform (fft) calculations on the individualscan data as measures will yield the type of deformations and theirdimensions in order to reproduce accurate amplitudes and frequencies ofsurface defects encountered. These are a description of the microscopichills and valleys on the surface, the dimensions of them, and thefrequency of each type. The magnitude and frequency of these topographyfeatures can then be compared to settable limits in order to effectchanges in process control. This Topography method, coupled with theprevious methods, will be used to implement a feedback mechanism for theTissue Process Control as well as the Yankee Coating Process control.

An interesting side effect of the Yankee coating Chemistry is that it istranslucent. Although some lensing effect will occur, a secondaryreflection will occur on the Yankee Drier machined metal surface. If itis perfectly flat, and ignoring the lensing affect (double passingthrough the Yankee Coating) as negligible, the reflected rays receivedon the CCD array should occur exactly shifted from the Coating Surfacereflections equal to the dimension of the exact coating thickness. Inother words, if the true thickness of the coating is 0.010″ thick, thenthis secondary Yankee Surface reflection should be exactly received bythe pixel location 0.010 inches upward of the original reflection causedby the initial Coating refection. Of course, as the surface of each(Coating Surface and Yankee Surface) become worn, or out of tolerances,the dispersion of the beams will be evaluated with fft calculations, asdescribed previously, in order to affect process control and ormaintenance of both surfaces. FIG. 6 has been included for clarity.

Correcting for the Alignment of the Detector Bank Array to the YankeeDrier

In order to be able to resolve the desired integrity of the signalscoming in from the detector bank array for the Yankee Drier mechanism,we will have to be able to re-evaluate, continuously, the registrationof the Detector Bank Array of sensors, per this discussion, to theMachined Yankee Drier Surface. This surface wears with use. Taking theDetector Bank and Rail system out for Yankee Drier maintenance willinject an associated misalignment when reinstalling the Detector BankArray back into its scanning position. Therefore, it is necessary tocreate a means of evaluating the true alignment of the Detector BankArray to the Yankee surface.

FIG. 7 describes a means to evaluate the distance from the Detector Bank

Array to the Yankee surface by Chromatic (color) Aberration. ColorAberration occurs due to that fact that different wavelengths of light,traveling through a lens, exhibit a different index of refraction atthese differing wavelengths. Since this is true, different wavelengthswill experience different focal points based on:

-   -   Power of a lens=((Refractive        Index−n0air)/n0air)*((1/radiuscm1)−(1/radiuscm2))    -   Where:    -   n0air=1    -   radiuscm2=1 for Plano convex    -   radiuscm1 from lens in cm    -   chromatic dispersion=dn/dwl=(change in refractive index/change        in wavelength)    -   d=change, n=refractive index, wl=wavelength    -   For example:    -   for N-K5 optical glass lens @ 25 mm diameter×200 mm fl        dn/dwl=−0.0732/micron

In using this principle, it is possible to create a distance finder byimplementing the scheme described in the next diagram. This technique iswell known and documented. However, we are mentioning it here as part ofthe mechanism for alignment detection, which is part of this invention.From the components chosen, and using a spectrometer to analyze thereturning light, we should be able to resolve distances down to 0.001″from the Yankee Drier Surface to the Detector Bank Array. The truedistances being derived will allow us to implement corrections formisalignment in the instrument data in order to maintain dynamic realtime calibrations.

The theoretical resolution for the components chosen should be0.383/((1000 nm-200 nm)/(0.3 nm/pixel)) divisions or 0.00014 incheshowever, a resolution of 0.0014 inches is expected.

Basically, the closer the Yankee Drier Surface is to the Detector BankArray, the more short wave will be in focus and will be reflected backwhere as if further away, more red light will be in focus at thatdistance and be reflected back toward the Spectrometer input.

A Further Description of the Creping Station

In FIGS. 8-12, a holder houses the Creping Blade as well as the DoctorBlade underneath. The pressure of the blades against the Yankee Driercan often be critical. As these Blades wear, their effect on the PolymerCoated Yankee Drier Surface and the Creping Blade's ability to affectthe proper folding of the tissue as it hits the edge of this Crepingblade diminishes. Therefore, it can often become necessary to monitorthis part of the tissue process.

A measurement of the folding process (as the tissue hits the CrepingBlade) is normally expressed in folds per inch. As the proper number offolds per inch (FPI) increases beyond a the desired target FPI , theTissue will become weak losing its strength properties diminishinginter-fiber bonding to a level that is unacceptable. Conversely, if theFPI decreases the pliability of the product will diminish causing theproduct to be not as soft as would be desired. Maintaining the desiredequilibrium is beyond the scope here but being able to measure the FPTis a required aspect of this invention. Since the Tissue Paper istraveling at a speed of around 27 inches per second, or at about 70miles an hour, when it encounters the Creping Blade edge, the energydeparted onto the Creping Blade edge is substantial. This is evident athow quickly the edges wear even though the edges are made of hardenedmetal alloy tips. When conditions are just right for this process, it issaid that the tissue will explode at the Creping Blade. Under thisprinciple, the Creping process is certainly going to carry thisvibrational energy from the tip of the blade to its absorbing point,which is the holder. During this process, the plane (width) of the bladeis going to oscillate as the wave moves through it. These waves will beat a frequency which equals this explosion frequency or a harmonic thereof. In other words, it will become a Speaker humming a tune equivalentto the folds per inch of the Creping process. Installing a Piezoelectricmicrophone device near, or in close contact, along the oscillating planeof the blade will enable us to measure this frequency. Implementing adual twin T notch type of filtering on the raw analog signals (removesunwanted frequencies, which will simplify the equations) and furtherapplying Fast Fourier Transforms on the measures of data received willenable the derivation of the FPI (Folds/Inch) of the Tissue process.

It may be feasible to measure the Folds per inch of the Tissue by usinga CCD device and lighting in a high contrast mode. It could be feasibleto, mathematically, pull the FPI sine wave generated out of the signalsusing fft calculations.

As both Blades increase in wear, a noticeable temperature change shouldoccur due to the corresponding change in friction. Placing temperaturedetectors along the length of the Blade Planes should indicate theamount of wear as these temperature differential moves across the bladeplanes. In addition, if the Doctor Blade cuts through the YankeeCoating, the temperature rise will be quickly dramatic, indicating theneed for the immediate attention of the operator. This will be an audioalarm and an appropriate texting message to the operator.

The force of the blade assembly across the entire length of the YankeeDrier needs to be monitored. If the force exerted on the Blades is notcorrect, or if a hot spot develops during production, damage to thecoating and or Yankee Drier Surfaces will occur. The force exerted onthe blades and the blade assembly will cause a deflection on the bladeplane (width). Changes on this pressure during the process will occur asthe blades wear but also could arise for other reasons as well. Forinstance, if a wet spot is encounter in the tissue web. This conditionwill soften the coating slightly thereby decreasing the blade forceslightly. Many conditions can change this force in production. However,for the purposes of this invention, it is sufficient to say that changeswill occur and that those changes will need to be monitored.

The Hall Effect Method (see FIG. 8) takes advantage of a changing bladedeflection. This causes the blade assemble to become closer, or fartheraway, from the fixed magnets. As this happens, a measurable disturbanceshould occur in the magnetic flux generated by the magnets as receivedon the Hall Effect Sensor. The sensor is designed to read changes inmagnetic flux.

The Capacitive Load Cell shown in FIG. 9 works by passing a proportionamount of the square wave charging the outside plates to the centerplate. If the outer plates are charges with a square wave atapproximately 500 kHz to 1 MHz and where these square wave are out ofphase or phase shifted by 90 degrees from each other, then at zerodeflection of the inner plate the resulting signal output on the middleplate should be 45 degrees phase shifted position between the upper andlower plate. As the middle plate deflects toward the upper plate due toload, the phase shift of the middle plate will shift toward that of thephase shift of the upper plate. If the deflection is negative, the phaseshift on the middle plate will shift in the direction of the lowerplate.

Load Cells (see FIG. 10) provide a very accurate way to measure thedeflection and forces on the blade directly. It works by measuring forceby deflecting a strain gauge printed on a metal form. There use is welldocumented in the literature and as they are a standard industrialmethod of measuring force, we will not go into further detail about thismethod since it is obvious.

The Capacitive Plate method (see FIG. 11) uses the property where twoplates will transfer a charge based on the dielectric constant and thedistance between two plates. Since the dielectric constant is equal to 1for air, the distance between the Creping Blade and the charging platewill be a direct function of the degree of deflection between thecharging plate and the Creping blade. Therefore, this method isfeasible. The system will vary with changes in temperature so atemperature correction mechanism will be used. Also, since the air in apaper mill is extremely humid, and considering that the dielectricconstant of water is 80.1 (at 20 C) compared to that of air which is 1,compensation for the humidity of the water vapor between the blade andthe charging plate will be required as well.

The LED intensity method (see FIG. 12) is also very feasible. This worksby sending out a quantum energy of light, which will bounce of theCreping Blade surface and then be received by the photo diode receiver.As the force on the Creping blade causes deflection, the distancebetween the Creping blade and the emitter-receiver pair will change.This will present a measureable change in signal, which is proportionalto the deflection.

As is now apparent, are several ways this can be monitored. A Halleffect sensor, to measure changes in magnetic field, could be used.Creating a magnetic field above and below the Blades assembly willinitiate measurable disturbances in that field as blade deflectionoccurs. This assumes an Iron component to the metallurgy of the blades.

Load cells could be installed which, as deflection occurs, will cause aproportional force to be applied on the load cell device. Placing loadcells every inch along the Blade planes should give accurate descriptionof the blade pressures at any point.

Capacitive change type of detection can be used which works on theprinciple of changing the distance of the gap between two or more plateswill change the value of the microfarad value. If the Creping Blade actsas one plate while another plate mounted above the blade acts as acharged reference, as the blade deflects due to a changing pressure, thecapacitor value of these plates will change proportionally. This changecan be measured and amplified.

Finally, a changing light intensity can be employed, which will measurethe changing distance between the Creping blade and the emitter-receiverpair. This changing distance is proportional to the force on the bladeassembly.

Roll Up Inspection Station

This station (see FIG. 13) will consist of a x axis linear ball guide totransverse a moisture detecting camera as descried earlier and an IRtemperature sensor across the web to record the final product moistureand the temperature as the product is being rolled up. Both of thesedevices have been described earlier in the Yankee Inspection Station areof the same type. They are both used in the same mode as describedpreviously. This station includes an encoder to keep track of the linearfeet contained in each roll. As the rolls are ended and a new roll isstarted, quality reports will be stored permanently on the system harddrive with a date and time stamp as well as a number so that thesepermanent records will be available per each roll at any timethereafter. A printable version can be printed if desired by thecustomer.

A Final Solution

The final solution (see FIG. 14) in addressing the Quality Controlproblems is to implement what we have learned from all of these devices.Since the actual addition of the Coating Chemistry is so critical inachieving the successful output of quality tissue. Implementing micromanagement of the spray application by measuring and controlling eachspray nozzle is imperative. This can be accomplished with a bank of flowmeters and proportional flow rate valves off a manifold of higherpressure. If the manifold is at a higher pressure than that needed atthe nozzles, we can shift the main pressure drop to the proportionalvalve creating, and measuring (through the flow meters) controllableflow rates at each nozzle. This will allow the system to implementcorrections in flow rates in order to keep the coating in propercondition. It will also allow us to repair bad areas as well.

In evaluating the residual Coating thickness and the residual componentconcentrations of that coating, then correlating this data to the linearmovement across the Yankee Drier surface by a linear ball screw device,we will be able to develop a complete profile of the Yankee Drier Coatedsurface in real time. Minute changes in the integrated absorptionresponse, Topography, temperature, and moisture content, will beproportional to the quality of the residual coating and to the qualityof the tissue being made. We should be able to vary the original recipecomponent concentrations in order to effect quality enhancements in themanufacturing of the tissue product in real time, while dynamicallymaintaining the desired quality of the coating as well. By passing theDetector Bank Array back and forth along the Yankee Drier surface, wewill be able to develop a surface profile. This Profile will pin pointproblems in manufacturing such as correcting deficient areas of Coatingby adjusting the recipe, changing flow rates, and warning the operatorof problems elsewhere in the process that could affect quality ordowntime. An example of the latter would be a wet spot cause by a vacuumproblem on the felt or a dry spot caused by insufficient fiber contentin the stock being fed at a location in the head box as well as amultitude of other process problems. In any case, Correcting the issuesmentioned will lead to better overall Quality, decreased down time, andincrease all of our profits, and just as a subtlety... initiate apropensity toward longer Blade life . . . a successful proposition forus all.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. The terminology used in thedescription herein is for describing particular embodiments only and isnot intended to be limiting. As used in the specification and appendedclaims, the singular forms “a,” “an,” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth as used in the specification and claims are to beunderstood as being modified in all instances by the term “about.”Accordingly, unless otherwise indicated, the numerical properties setforth in the specification and claims are approximations that may varydepending on the desired properties sought to be obtained in embodimentsof the present invention. Notwithstanding that the numerical ranges andparameters setting forth the broad scope of the invention areapproximations, the numerical values set forth in the specific examplesare reported as precisely as possible. One of ordinary skill in the artwill understand that any numerical values inherently contain certainerrors attributable to the measurement techniques used to ascertain thevalues.

Having described the disclosure in detail and by reference to specificembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of thedisclosure defined in the appended claims. More specifically, althoughsome aspects of the present disclosure are identified herein aspreferred or particularly advantageous, it is contemplated that thepresent disclosure is not necessarily limited to these preferred aspectsof the disclosure.

What is claimed is:
 1. A coating system and method thereof to takecontrol and correct the application of the release coating chemistry toinsure: the release coating chemistry is at the proper mix ratio asprogrammed by a recipe set point which may be adjustable by theoperator, the release coating is being applied in the proper thicknessacross the Yankee dryer surface at all times, increase and decrease theproportional valves at each nozzle in order to compensate for, andmaintain, a constant flow rate independent from variations in supplypressure, increase and decrease the flow rate in order to compensate forvariations in production speed (ft/min), detect and report graphicallyareas that are not coated properly if the system cannot correct aspecific problem, provide a graphical view of the concurrent productionas to speed, flow rates, release coating thickness, and Yankeetemperature profile over the entire surface, extend the life of thecreping and doctor blades, decrease maintenance on the spray nozzles,and translate the production data obtained into clear visual results andwarn operators in an audio, and visual (graphical) manner of processproblems.
 2. A paper machine substantially as shown and describedherein.
 3. A method of operating a paper machine substantially as shownand described herein.